Hitachi Koki Co., Ltd.

Hitachi Printing Solutions, Ltd.

Other

Ricoh Printing Systems, Ltd.

Hitachi, Ltd.

Masayoshi Ishii

Teruaki Mitsuya

Keisuke Kubota

Hiroyuki Mabuchi

Hisao Okada

Shinichi Akatsu

Tsuneaki Kawanishi

Koji Kato

Hiroyoshi Matsumoto

Hisayoshi Kato

Natsuki Kuribayashi

Shintaro Yamada

Shinya Kobayashi

Kenichi Ito

Nobuyoshi Hoshi

Yasuo Takuma

Seiji Maruo

Ryuuichi Shimizu

Katsuhiko Suzuki

Masami Ishikawa

Hideki Ando

In an image forming method, when viewed from the moving direction of a photosensitive bodythere is disposed, on the upstream side, a first developing rolleropposed to and adjacent to the photosensitive bodyand rotatable in the opposite direction to the photosensitive bodywhile the peripheral speed ratio of the rollerto the photosensitive bodyranges from 0.8 to 2.0; on the downstream side of the rollerthere is disposed a second developing rollerrotatable in the same direction to the photosensitive bodywhile the peripheral speed ratio of the rollerto the photosensitive bodyranges from 1.05 to 2.0; and the shape coefficient SFof the toners of two-component developing agent ranges from 120 to 170, while the shape coefficient SFranges from 110 to 130.

Image forming method and image forming apparatus

A position where a transport amount regulation member is opposed to a developing roller is in an area wherein the magnetic flux density in the tangent line direction becomes 95% or less of the maximum value upstream in the developer transport direction from the position at which the magnetic flux density in the normal direction formed by two magnetic poles on both sides of the transport amount regulation member on the sleeve roller surface of the developing roller becomes 0 gausses and is in an area wherein the magnetic flux density in the normal direction becomes 90% or less of the maximum value of the upstream pole in the developer transport direction.

Developing apparatus and electrostatic record apparatus

A transfer member transporting section is disposed so as to bring a tip end of a transfer member into contact with a peripheral face of a transfer rotary member before the tip end of the transfer member enters a nip area. A bias power supply has a polarity inverting function of, during a period from a timing when the tip end of the transfer member is brought into contact with the transfer rotary member by the transfer member transporting section, to that when the tip end of the transfer member enters the nip area, applying a voltage of a polarity which is identical with that of a toner, to the transfer rotary member, and after the tip end of the transfer member enters the nip area, applying a voltage of a polarity which is opposite to that of the toner, to the transfer rotary member.

Image forming apparatus with transfer bias inverting function

A developing unit in an electro-photographic apparatus such as a printer, a facsimile and a copier for actualizing an image employing colored particles such as toner, and more particularly to a developing unit for forming a toner image on the surface of a photosensitive body. The developing unit includes a plurality of developing rollers each having a core and a sleeve. The sleeve accommodates the core. The plurality of developing rollers include a first developing roller and a second developing roller. The sleeve for the first developing roller is rotated to move in the same direction as a moving direction of the surface of the photosensitive body. The sleeve for the second developing roller is rotated to move in an opposite direction to the moving direction of the surface of the photosensitive body. The core of only one of the plurality of developing rollers is driven in rotation while the other core is fixed. Alternatively, a magnetic pole of one of the developing rollers is placed at an opposing position where the developing rollers mutually oppose while an intermediate portion between two poles of the second developer roller is placed at the opposing position.

Electro-photographic developing unit

A transfer flow-in current which flows from a transferring device into an image carrier, a separation flow-in current which flows from a separating device into the image carrier, an aperture width in the recording member transporting direction of an aperture of the transferring device, and an aperture width in the recording member transporting direction of an aperture of the separating device are set so as to have the relationship: separation flow-in current&equals;transfer flow-in current&times;(transfer aperture width/separation aperture width).

Electrophotographic apparatus including transferring device

An electrophotographic cluster printing system for performing printing by using a plurality of electrophotographic recording apparatuses such as printers, facsimile machines or copying machines each capable of manifesting an image by using colored particles such as toner. The electrophotographic cluster printing system includes a plurality of electrophotograhic recording apparatuses each including a photoconductor, a charger, an exposure device, a developing device, and an image quality controller for detecting a factor concerning image quality and controlling image quality of an output image on the basis of information of the detected factor. In the system, at least two of the electrophotograhic recording apparatuses is used for printing one job and image quality of any one of the electrophotograhic recording apparatuses is controlled on the basis of detected information of the other electrophotograhic recording apparatuses.

Electrophotographic cluster printing system with controlled image quality

A print control method of an electrophotograph in an image formation apparatus including at least a photoconductor, a charger, a light exposure unit, and a developing device for forming a background area and an image area on the photoconductor using the charger and the light exposure unit and detecting a potential of the image area after transfer and controlling a developing electric field, thereby printing an electrophotograph, includes lowering the percentage of toner covering the image area on the photoconductor when the potential is detected.

Print control method of electrophotograph and image formation apparatus with potential sensor using the method

An image formation apparatus for keeping secularly stable image quality for all image patterns if change in the charge amount of a developer caused by environment variation or over time or change in the photoconductor characteristic occurs in electrophotographic record apparatus. A test patch image formed on a photoconductor by a parallel electric field is detected by an image density sensor, the developing bias and the photoconductor surface potential are controlled so that the density detected by the image density sensor becomes constant, a test patch image formed on the photoconductor by a peripheral electric field is detected by the image density sensor with the control condition of the image density sensor maintained, and the light application amount in which an image area of a several-dot width adjacent a blank paper part is exposed to light is controlled so that the density detected by the image density sensor becomes constant.

Control method of an electrophotographic record apparatus and image formation apparatus including controlling developing bias and photoconductor surface potential

An image forming apparatus restricts disturbance of a potential patch in the case where a potential sensor for detecting the potential patch is provided downstream of a developing device of a multiple developing roller type so as to enable stable reproduction of a high quality image for a long period. The apparatus includes a potential sensor provided downstream in the moving direction of the image carrier relative to the developing device for detecting a potential on the image carrier, and a controller for setting the developing bias to a value restricting disturbance of a potential portion as an object for potential detection by the potential sensor by the developer when the potential portion passes across the developing device.

Image forming apparatus

In an image forming apparatus for charging a photosensitive body, changing the light exposure amount in at least three levels at exposure to light, thereby forming an electrostatic image made up of a high-potential part, a low-potential part, and an intermediate-potential part therebetween on the photosensitive body, and normally developing and inversely developing the electrostatic image using toners different in charge polarity for forming two types of toner images on the photosensitive body, a first developer used with a first toner image developing unit has electric resistance changed within 10% in the change range of applied voltage to the developer as the difference between a surface potential of the photosensitive body and a developing bias voltage.

Image forming electrophotography apparatus and magnetic developing unit

In an image forming apparatus, the developing unit includes two developing rollers whose rotational directions are different from each other, and a bias potential of the developing roller (first developing roller) located upstream in the rotational direction of the photosensitive member is selected to be a potential, which is in value between a bias potential of the developing roller (second developing roller) located downstream in the same direction and a background potential.

A first developing unit comprising a plurality of developing rolls including a developing roll whose rotation direction is matched with the move direction of a photosensitive body and a developing roll whose rotation direction is made opposite to the move direction of the photosensitive body.

Color image forming method and device using potential division development

An electrophotographic printing apparatus using electric potential dividing development processing without the occurrence of primary fringe and fringe caused by auxiliary exposure has reverse electric fields causing primary fringe and fringe caused by auxiliary exposure adjusted to be nearly equal to each other. The auxiliary exposure is applied to an area surrounding one image, and an electric potential of an intermediate electric potential zone is brought close to a bias electric potential of another image which is not subjected to auxiliary exposure. Further, a white portion to produce a reverse electric potential therein at the rear end of an electric potential portion to be developed with toner, relative to a rotating direction of a developing roller, is exposed with a light intensity forming an electric potential between an electric potential developing an image with toner and the intermediate electric potential, and portions at the front end and the sides are exposed with a light intensity forming the intermediate electric potential.

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Ibaraki, Japan

Masayoshi Ishii